Serendipita indica
(former
Piriformospora indica
) is a non-obligate endophytic fungus and generally a plant growth and defence promoter with high potential to be used in agriculture. However,
S. ...indica
may switch from biotrophy to saprotrophy losing its plant growth promoting traits. Our aim was to understand if the free-living stage growth conditions (namely C availability) regulate
S. indica
’s phenotype, and its potential as plant-growth-promoting-microbe (PGPM). We grew
S. indica
in its free-living stage under increasing C availabilities (2–20 g L
–1
of glucose or sucrose). We first characterised the effect of C availability during free-living stage growth on fungal phenotype: colonies growth and physiology (plasma membrane proton pumps, stable isotopic signatures, and potential extracellular decomposing enzymes). The effect of the C availability during the free-living stage of the PGPM was evaluated on wheat. We observed that C availability during the free-living stage regulated
S. indica
’s growth, ultrastructure and physiology, resulting in two distinct colony phenotypes: compact and explorer. The compact phenotype developed at low C, used peptone as the major C and N source, and displayed higher decomposing potential for C providing substrates; while the explorer phenotype developed at high C, used glucose and sucrose as major C sources and casein and yeast extract as major N sources, and displayed higher decomposing potential for N and P providing substrates. The C availability, or the C/N ratio, during the free-living stage left a legacy to the symbiosis stage, regulating
S. indica
’s potential to promote plant growth: wheat growth promotion by the explorer phenotype was ± 40% higher than that by the compact phenotype. Our study highlights the importance of considering microbial ecology in designing PGPM/biofertilizers. Further studies are needed to test the phenotypes under more extreme conditions, and to understand if the
in vitro
acquired characteristics persist under field conditions.
Eucalypt cultivation is an important economic activity worldwide. In Portugal, Eucalyptus globulus plantations account for one-third of the total forested area. The nutritional requirements of this ...crop have been well studied, and nitrogen (N) is one of the most important elements required for vegetal growth. N dynamics in soils are influenced by microorganisms, such as diazotrophic bacteria (DB) that are responsible for biological nitrogen fixation (BNF), so the aim of this study was to evaluate and identity the main groups of DB in E. globulus plantations. Samples of soil and root systems were collected in winter and summer from three different Portuguese regions (Penafiel, Gavião and Odemira). We observed that DB communities were affected by season, N fertilization and moisture. Furthermore Bradyrhizobium and Burkholderia were the most prevalent genera in these three regions. This is the first study describing the dynamic of these bacteria in E. globulus plantations, and these data will likely contribute to a better understanding of the nutritional requirements of eucalypt cultivation and associated organic matter turnover.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Crop management systems influence plant productivity and nutrient use efficiency, as well as plant growth-promoting rhizobacteria (PGPR), which are known to influence the growth of plants via ...phytohormone production, phosphate solubilization, nitrogen (N) fixation and antimicrobial activity. The objective of this study was to compare the influence of two crop management system on microbial PGPR features. PGPR isolated from the rhizospheres of
Carica papaya
L. grown under two distinct management systems (conventional and organic) were identified and characterized. The 12 strains most efficient in solubilizing inorganic phosphate belonged to the genera
Burkholderia
,
Klebsiella
, and
Leclercia.
N fixation was observed in the strains
B. vietnamiensis
from the conventional farming system and
B. vietnamiensis
,
B. cepacia
and
Leclercia
sp. from the organic farming system. The
B. vietnamiensis
,
B. cepacia
,
Klebsiella
sp. and
Klebsiella
sp. isolates showed antifungal activity, while
Leclercia
sp. did not. The strains
B. vietnamiensis
and
Enterobcter
sp. (isolated from the conventional farming system) and
Klebsiella
sp. (isolated from the organic farming system) were efficient at solubilizing phosphate, producing phytohormones and siderophores, and inhibiting the mycelial growth of various phytopathogenic fungi (
Botrytis cinerea
,
Pestalotia
sp.,
Alternaria
sp.,
Phoma
sp.,
Fusarium culmorum
,
Geotrichum candidum
). Physiological differences between the isolates from the two crop management regimes were distinguishable after 10 years of distinct management.
Parchments are important documents that give testimony for History; therefore these materials should be respected and preserved. Considering incremental biodeterioration problems that have to be ...faced daily, the Archive of the University of Coimbra (AUC) is involved in different scientific projects in order to evaluate and determine new methods for document decontamination and preservation.
The aim of this study was to evaluate gamma radiation effects on the colour and texture of the AUC parchment documents. The assessment of these effects was used to estimate the maximum gamma radiation dose (Dmax) that could guarantee parchment documents′ decontamination treatment, without significant alteration of their physical properties. Parchment samples were exposed to gamma radiation doses ranging from 10 to 30kGy. The texture and colour of samples were assessed before and after the irradiation procedure, using a texture analyser and an electronic colorimeter. Hardness and springiness were determined based on texture spectra. Lightness (L⁎), Chroma (C), greenness vs. redness (a*) and yellowness vs. blueness (b*) values were obtained from colorimetric measures. Results indicate no significant effects of gamma radiation on the texture and colour of parchment for the studied doses.
► Study on the effects of gamma radiation in parchment physical properties. ► Evaluation of the uniformity of parchment samples′ physical parameters. ► Proposal of a maximum gamma radiation dose for parchment decontamination treatment.
•PSB from papaya’s conventional and organic farming were grown in monoculture or in pairs.•Organic acids production was not related with Pi solubilisation.•There was no cooperation in pairs with only ...PSB isolated from conventional farming.•40% of the pairs with PSB from organic farming cooperated in Pi solubilisation.•Interactions output (cooperation or antagonism) was not phylogenetically determined.
We tested the legacy of the farming system (conventional or organic) on the interactions among phosphate solubilizing bacteria (PSB) and phosphate (Pi) solubilisation. We determined the in vitro Pi solubilisation and production of organic acids by nine PSB (four from conventional and five from organic farming) isolated from the rhizospheres of Carica papya, grown in monoculture or in pairs (66 combinations). When grown in monoculture, PSB isolated from conventional farming solubilised more Pi, but when grown in pairs, these PSB solubilised the least Pi. Furthermore, when the pairs included only PSB isolated from conventional farming, no Pi-solubilising cooperation was observed, that is, Pi solubilisation by pairs was lower than in monoculture. When PSB isolated from organic farming were present in the pairs, ∼40% of the combinations resulted in Pi solubilising cooperation. Organic acid production was not related with Pi solubilisation. Our work demonstrated the existence of a farming system legacy influencing the biotic interactions among PSB, and that the output of the interactions (cooperation or antagonism) was not phylogenetically determined. Data highlighted that biotic interactions should be considered when screening for potential plant growth promoting bacteria.
•Under low N, inoculated Dimorphandra wilsonii seedlings grew more despite no nodules.•N fixation was suggested only in the presence of the symbionts under limiting N.•Plant 13C, substrate’s C and ...respiration suggest C economy in microbial recruitment.•Belowground symbiotic microbes mitigated plant-plant competition.
Dimorphandra wilsonii, a Cerrado endemic Fabaceae tree, is threatened by land-use changes. The few remaining individuals occur in areas dominated by alien grasses like Urochloa decumbens. We tested the impact of nitrogen (N) availability and symbionts’ presence on mitigating the effects of competition from U. decumbens.
Dimorphandra wilsonii seedlings were 50-week pot-cultivated under limiting (3mM) or non-limiting (10mM) N, with or without U. decumbens, and inoculated or not with a N-fixer (Bradyrhizobium sp.) and an arbuscular mycorrhizal fungus (AMF – Glomus etunicatum), both forming symbioses in the field.
Since D. wilsonii seedlings grew more and ‘lost’ fewer nutrients under the symbionts’ presence, symbionts mitigated plant-plant competition. Under limiting N, inoculated D. wilsonii seedlings grew more (despite no nodulation), but N fixation was only suggested when inoculated D. wilsonii seedlings competed with U. decumbens. D. wilsonii13C, and substrate’s carbon and respiration suggest that only the microbes performing key functions received plant carbon. Under non-limiting N, inoculated D. wilsonii seedlings became enriched in 13C, substrate accumulated carbon and microbial respiration increased, suggesting a more generalist microbial community. Data suggest inoculating D. wilsonii seeds/seedlings with AMF and N-fixers as a conservation measure. However, long-term field-studies need to confirm these conclusions.
The fungistatic activity of six aqueous extracts of plants were tested against
Aspergillus candidus,
Aspergillus niger,
Penicillium sp. and
Fusarium culmorum. The plants were, chamomile (
Anthemis ...nobilis L.), cinnamon (
Cinnamomum verum J. Presl.), French lavender (
Lavandula stoechas L.), garlic (
Allium sativum L.), malva (
Malva sylvestris L.) and peppermint (
Mentha piperita L.). The more concentrated extracts of chamomile and malva inhibited totally the growth of the tested fungi with malva being the most effective one.
Objective Microbial communities are a central component of trophic dynamics and biogeochemical processes on coastal systems, since most of the processes in sediments are mediated by microorganisms ...and carried out by enzymes. Microorganisms play a key role in decomposition processes in salt marsh sediments, although the significance of microbial dynamics is largely unexplored. A culture-dependent (Ecoplate) and a culture-independent (extracellular enzyme activity EEA) approaches were evaluated in their ability to distinguish the catabolic potential among sediments from Tagus estuary salt marshes with different proximities to anthropogenic sources. Methods Ecoplate was used to analyse the salt marsh community-level physiological profiles (CLPPs). Results were expressed as the net area under the curve for each of the 31 response wells over a 3-day incubation period in two sediment horizons. The catabolic profiles for salt marsh samples were analysed by Principal Component Analysis (PCA) and hierarchic clustering methods. EEA was analysed by fluorescein diacetate (FDA) hydrolysis in two sediment horizons. The FDA is catalysed by extracellular enzymes, i.e. esterases, lipases and partially by proteases. Results were expressed as μg g-¹d wt h-¹. Results and Discussion In this study the CLPP and EEA data were not generally correlated. In Corroios salt marsh only in surface sediments higher net areas corresponded to higher extracellular enzymatic activity, and in Alcochete deep sediments lower net areas corresponded to lower enzymatic activity. Although EEA profiles more directly reflect the inherent activity of resident community in each salt marsh sample, the CLPP profiles provide better assessments of diversity.
Borrelia and Rickettsia bacteria are the most important tick-borne agents causing disease in Portugal. Identification and characterization of these circulating agents, mainly in recreational areas, ...is crucial for the development of preventive measures in response to the gradually increasing exposure of humans to tick vectors. A total of 677 questing ticks including Dermacentor marginatus, Rhipicephalus sanguineus, Ixodes ricinus, Hyalomma lusitanicum, H. marginatum, and Haemaphysalis punctata were collected in a Safari Park in Alentejo, Portugal, to investigate the prevalences of infection and characterize Borrelia and Rickettsia species. From a total of 371 ticks tested by PCR for Borrelia burgdorferi sensu lato (s.l.), of which 247 were tested for Rickettsia, an infection prevalence of 18.3% was found for B. lusitaniae and 55.1% for Rickettsia spp. Sequence analysis of positive amplicons identified the presence of B. lusitaniae (18.3%), R. monacensis strain IRS3 (51.7%), and R. helvetica (48.3%) in I. ricinus. R. slovaca (41.5%), R. raoultii (58.5%), and also B. lusitaniae (21%) were identified in D. marginatus ticks. One (5.9%) H. lusitanicum was infected with B. lusitaniae, and R. massiliae was found in one Rhipicephalus sanguineus. Coinfection was found in 7 (20%) I. ricinus and 34 (23.3%) D. marginatus ticks. We report, for the first time, simultaneous infection with R. helvetica and B. lusitaniae and also R. slovaca, the agent of TIBOLA/DEBONEL, with B. lusitaniae. Additionally, 6 isolates of B. lusitaniae were established, and isolates of Rickettsia were also obtained for the detected species using tick macerates cultured in mammalian and mosquito cell lines. This report describes the detection and isolation of tick-borne agents from a Portuguese Safari Park, highlighting the increased likelihood of infection with multiple agents to potential visitors or staff.
The increasing frequency by which the production of paralytic shellfish toxins (PST) by freshwater bloom-forming cyanobacteria is being noticed world-wide raises the possibility of PST ...bioaccumulation by freshwater mussels. This study evaluates PST accumulation and depuration by the freshwater mussel
Anodonta cygnea exposed over a 14-day period to high densities (mean=1.4×10
9
cells
l
−1, S.D.=0.29×10
9
cells
l
−1) of the toxic cyanobacterium
Aphanizomenon issatschenkoi (corresponding to a mean toxin concentration of 25.5
nmol PST
l
−1, S.D.=9.9
nmol PST
l
−1). Mussels were subsequently detoxified either by starvation or by feeding on the non-toxic green-algae
Ankistodesmus falcatus. Filter feeding activity and toxin uptake by the mussels were followed by cell counting and toxin analysis in water samples taken before and after each daily water renewal. The accumulation and depuration of PST as well as the anatomical distribution of toxins were monitored throughout the experiment by HPLC analysis of mussel extracts. Mussels fed the toxic cyanobacterium removed on average 65.3% of cells and 40.36% of total PST daily provided. Daily rates of cell clearance (% of initial) were negatively correlated with the amounts of PST daily provided (but not with the amount of cells). This suggests a negative effect of toxins on the feeding behaviour of mussels. Small amounts of toxins could be detected in the mussels after the second day of exposure, reaching a maximum of 26
μg PST
100
g
−1 by day 7. The viscera contained the greatest proportion of toxins (78%) at the start of the toxification. However, increasing amounts of PST were found in the remaining tissues (gills, mantle and foot) over time. Toxins detected in the mussel extracts were the same provided in the dietary
A. issatschenkoi. Nevertheless, mussels showed a higher proportion of saxitoxin and decarbomoylsaxitoxin and a lower proportion of gonyautoxin-5 than the fed cyanobacterium. Similar depuration efficiencies were observed among starved individuals (6.9% day
−1) and those fed with
A. falcatus (8.2% day
−1) indicating that both treatments had comparable effects on toxin metabolism. Mussels showed a typical S shaped depuration kinetics curve consisting of a first short period of slow toxin decay followed by a rapid loss and a subsequent slower release of toxins. Trace to undetectable levels of PST were found in mussels after the 14-day depurating period. Although freshwater mussels are not widely consumed by humans, their capacity to accumulate PST points to the risk of PST propagation through the food chain of freshwater ecosystems via filter-feeding mussels.
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